1. Field of the Invention
The present invention relates to backup storage services in general, and more particularly relates to techniques for backup storage with reduced data redundancy.
2. Description of the Related Art
Backup servers enable users of data systems to store copies of data for safekeeping. Users may have working data on a system such as a primary data server. The users may wish to make a backup copy of the data, so that the backup copy is available in case of equipment failure or in case of user errors that can corrupt or destroy the data stored on the primary data server. In some situations, users may wish to have the backup data stored in a remote location, so that a local catastrophe such as a fire or weather-related incident that affects the primary data server is not likely to affect the remote location.
Operators of backup servers may wish to ensure that their storage systems are used in an efficient-manner. One technique for increasing the efficiency of a storage system is to avoid storing duplicate copies of data. This technique is generally thwarted, however, when users encrypt data prior to submission for backup storage. In such situations, a backup storage server may not be able to determine whether or not two portions (or “chunks”) of data carry the same contents, since the contents are obscured by the encryption. The interest of users in protecting their data by encryption can thus clash with the interest of operators in making efficient use of their storage systems. It would be helpful to have techniques that furthered both of these interests.